- Barebones world (just some land)
- Console output, relevant debug text
- Simple collision/Input
- More complex UI
- Refine World
- Refine UI
- Repeat 5-6 until gold
In a production environment normally you have a set of features you're responsible for, so knowing what to work on is rarely an issue (esp. with publishers )
The advantage of working indie is that once things are working on a very basic level, you can decide what you want to do when you want to do it.
If I could offer some advice though, try not to be too jumpy between systems. Lots of bugs happen that way.